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If the radius of a right circular cylinder open at both the ends, is decreased by 25% and the height of the cylinder is increased by 25%. Then the curved surface area of the cylinder thus formed
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- remains unaltered
- is increased by 25%
- is increased by 6.25%
- is decreased by 6.25%
- remains unaltered
Correct Option: D
| Effective percentage change = |  | x + y + |  | % | |
| 100 |
| = | | - 25 + 25 - | | % | |
| 100 |
= –6.25%
Negative sign shows decrease.
